In 2015, the World Health Organization’s cancer agency declared glyphosate weed killer to be a probable human carcinogen, in a move that alarmed the agrochemical industry and gardeners around the world.
The assessment that was conducted by the International Agency for Research on Cancer (IARC) of glyphosate, which is used in Roundup and other herbicides with estimated sales of $6 billion, was of special concern to Monsanto (now owned by Bayer AG). Monsanto was the company that first brought glyphosate to market under the name Roundup in the 1970s.
More than 80% of GM crops around the world have been genetically engineered to be grown with glyphosate.
The IARC does not have a regulatory role and its decisions do not necessarily lead to restrictions or bans. But environmental groups have used this ruling to apply pressure on regulators in the US and overseas.
The IARC reached this decision based upon the views of 17 industry experts from 11 nations. They met in Lyon, France to review the carcinogenicity of five organophosphate pesticides. Europe did re-approve glyphosate for five years after the decision by the IARC was rendered, however.
Since Decision, IARC Under Fire
In 2018, the WHO cancer agency firmly defended its decision that glyphosate is a probable human carcinogen, despite reports from lawmakers in the US.
The IARC’s firm stance on the chemical has continued, and was revealed in a February 2018 hearing on Capitol Hill at the House Science, Space and Technology Subcommittee on Environment. Oregon Representative Suzanne Bonamici, ranking Democrat on the subcommittee, entered into the record several responses to IARC Director Christopher Wild had sent to the panel in 2018.
Wild criticized two Reuters stories that suggested the IARC evaluation, known as a monograph, had deleted key information. Both of the Reuters stories were cited in letters to the IARC by Republicans Lamar Smith and Andy Biggs, the respective chairmen of the full committee and Environment Subcommittee.
One claimed that Aaron Blair, an epidemiologist from the US National Cancer Institute, who was the leader of the glyphosate review, had excluded from the review new research that he knew would prove no link between the chemical and cancer.
This was because the IARC monographs are based upon fully independent scientific reviews of published material and no on the basis of unpublished data, Wild explained in a 2017 letter.
Under Smith, the Science Committee has criticized EPA regulations that are based upon ‘secret science.’ Thus, Wild stated in his letter, it is wrong to assert that Blair is in a position to keep out critical information from the IARC study on glyphosate.
Another story that was flagged by the Science Committee in 2017 claimed that IARC had omitted key evidence that went against the conclusion that glyphosate probably caused cancer in humans and edited a draft before it was released to the public.
Wild said the IARC defers all risk assessment and risk management to international and national bodies. It restricts itself to hazard identification as a scientific foundation to those steps.
Anna Lowit, who is a senior science advisor in the EPA’s Office of Pesticide Programs, has defended her agency’s risk assessment on glyphosate, which determined that the weed killer does not cause cancer.
- Carcinogenicity of tetrachlorvinphos, parathion, malathion, diazinon and glyphosate. The Lancet. (2015). Retrieved from https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(15)70134-8/fulltext
- WHO Declares That Glyphosate Herbicides Probably Cause Cancer. (2015). Retrieved from https://sustainablepulse.com/2015/03/21/who-declares-that-glyphosate-herbicides-probably-cause-cancer
- WHO Rebuts House Committee Criticisms About Glyphosate Cancer Warning. (2018). Retrieved from https://www.sciencemag.org/news/2018/02/who-rebuts-house-committee-criticisms-about-glyphosate-cancer-warning